A tiled display device is formed from display tiles having picture element positions defined up to the edge of the tiles. The method may be used to produce non-refractory metal oxides as well. Since variations in the offset error of the differential pressure sensor 20 caused by changes in the ambient temperature around the differential pressure sensor 20 is made small, the amount of change in the differential pressure across the PM trapper 11 can be measured more accurately, and a fault of the PM trapper 11 can be detected with improved accuracy.